a) Field of the Invention
The invention is directed to an arrangement by means of which the radiation of a plurality of laser diode lines is combined and shaped in order, for example, to couple into an optical fiber or into the end face of a solid-state laser rod. This is a laser diode line light source which can be advantageously used, for example, in laser surgery, laser material processing or for pumping solid-state lasers.
b) Description of the Related Art
Laser diodes are distinguished from other lasers particularly by their high efficiency which is, however, combined with high current densities that allow only very small dimensions and accordingly limited output power.
Therefore, in many cases of application in which a higher laser output is needed, it becomes necessary to use the radiation output of a plurality of laser diodes which are combined in a corresponding manner.
High radiation quality, which is determined by the dimensioning of the beam cross section and the far-field divergence of the radiation, is required particularly when the combined beam bundle is to be coupled into a device or optical element following downstream.
The cross section of the emission surface of approximately 1 .mu.m.times.100 .mu.m in laser diodes results in an asymmetrical cross section for the respective emitting beam bundle with a longitudinal axis of approximately one hundred times the length of the transverse axis. This asymmetry is multiplied in the case of the radiation of a laser diode line due to the arrangement of individual emission surfaces on a straight line along their longitudinal axes as is required for technological reasons and reasons relating to cooling technique. In addition to the resulting unfavorable beam geometry, there is the widely different divergence of the radiation in the longitudinal axis and transverse axis. As is well known, the divergence of the laser diode radiation in the direction of the transverse axis, perpendicular to the plane of the pn junction of the laser diode, is as much as 90.degree., whereas it amounts to only approximately 10.degree. in the direction of the longitudinal axis, that is, parallel to the plane of the pn junction. The highly asymmetrical beam geometry and the divergence of the beam bundle of a laser diode line results in exacting requirements for an arrangement for combining and shaping radiation that must ultimately generate a beam bundle adapted to the aperture of the optics following downstream in order to achieve high in-coupling efficiency.